Reversing valve mechanism



2 Sheets-Sheet 1 C. D. RUSSELL REVERSING VALVE MECHANISM Feb. 22, 1966 Filed Jan. 23, 1964 I Zi Feb. 22, 1966 Filed Jan. 25', 1964 C. D. RUSSELL REVERSING VALVE MECHANISM FIG.6.

2 Sheets-Sheet 2 INVENTOR f' l *i i /l gif, la"

United States Patent iO 3,236,441 REVERSING VALVE MECHANISM CarlD. Russell, 223 NW. 24th St., Oklahoma City, Okla. Filed Jan. 23, 1964, Ser. No. 339,755 12 Claims. (Cl. 230-54) This invention relates `to improvements in reversing valve mechanisms of the type disclosed and claimed in my Patent 2,699,153, patented January 1l, 1955, and is more particularly directed to improved construction of such a reversing valve mechanism, `designed to enhance the precision -and surety of operation.

While continuing experience with reversing mechanism, as disclosed in my aforesaid patent, has amply demonstrated that its principle of operation is sound, it was learned that the uniformity and precision of its performance suffered from the absence of any positive control over the exhaust valve.

VIt is theV principal object of the present invention to irn- Vprove the uniformity and surety of performance of such a reversing valve mechanism, according to my aforesaid patent, through the provision of means effective by securing the -inlet and exhaust portions together as a single component, allowing only unity of movement.

A more specific object of the invention is the provision of a reversing valve mechanism of stated character wherein a provision is provided to impart movement required in positioning the valve when the circumstances demand.

Another object of the invention is a means to limit the actuation of the above means.

Still another object of the invention is a means to release the cause of the above imparted movement and allow` the means to return to its normal position.

The above and other objects and advantages of the irnproved lreversing valve mechanism of the present invention will be apparent from the following detailed description thereof, taken with the accompanying drawings, wherein:

FIG. 1 is a longitudinal section, taken through a motorcompressor unit of the connected piston type, powered by elastic working fluids, which illustrates one application of the improved reversing valve mechanism of the invention.

FIG. 2 is a composite drawing of the component portions in entirety of the working portions of the improved reversing valve mechanism, in assembly layout.

FIG. 3 is a longiutdinal section, omitting the working parts of FIG. 2, taken through the partition which forms a housing with inter passages, bores and extrusions becoming a portion of the reversing valve mechanism.

FIGS. 4 through 6 are partial sectional drawings to disclose the various operating positions of the reversing valve mechanism, designating each operation and effect on either the valve or motor-compressor pistons.

FIG. 1 shows, in detail, `the reversing valve mechanism, mounted in a partition which divides the cylinders in which the pistons are mounted for reciprocating travel. It is to be understood, however, that the improved reversing valve mechanism of the present Vinvention may `also be employed as a means for distributing a working fluid, such 3,236,441 Patented Feb. 22, 1966 To illustrate the first of the above-described applications, reference is had to FIG. l wherein reference numerals 10 and 10u designate elongated cylinders, closed at their outer ends by heads 11 and 11a, which are penetrated by suction lines 12 and 12a, and discharge lines 13 and 13a. The interior space of the said cylinders 10 and 10a is divided by acentral partition 30, in which connecting rod 15 extends through the valve body 17, which is fitted with sliding sealing material at 21 and 21a and nuts 22 and 22a, forming the valve body end closures; and, connecting rod 15 is mounted at its ends in pistons 14 and 14a, which accordingly reciprocate in unison; that is to say, either of the pistons 14 and 14a is motivated in outward direction by the working fluid effective on its inner face, motion in like but inward direction being imparted to the other piston through the connecting rod 15.

The pistons 14 and 14a are the means by which the power source is transmitted to the compressor area, the inner faces being the motorsource `and the outer being the compressor areas.

FIG. 2 is a composite `drawing showing the component portions in entirety, of the working portion of the improved reversing valve body 17, including working fluid passages 17a, 17b, 17C, 17d, 17e, and 17f. Also, the reduced portions 17m, and 1711 on the outer ends of valve body 17 are threaded at 171' and 17j to receive nuts 22 and 22a. Cup-Shaped cylinders comprise exhaust valves 18 and 18a which are seated against shoulders 17g and 17h and include bores of diameters to fit on reduced portions 17m and 1711 of the valve body 17. Sleeves 20 and 21 lit on reduced portions 17m and 17n and bear against valves 18 and 18a. Pistons 19 and19a slide on sleeves 20 and 20u and are adapted to be encompassed by exhaust valves 18 and 18a to form sealed cavities or chambers. Sealing rings 21 and 21a, of the O type, t within nuts 22 and 22a to close the ends of the valve body 17. Sleeves 20 and 21 are notched in their forward peripheries, as at 20c, to communicate with uid passages 17g and 17h.

FIG. 3 is a sectional view of the dividing partition 30, disclosing inlet passage 30a, communicating with bore 40 and extending from -bore 40 to angular passages 30h and 30e, which communicate with inner faces of the partition to form, together the inlet passageway. Exhaust valves 18 and 18a are provided to form an enclosure for bore 40, at passages 40d and 40C, to seal valve 17 from the inner portions of the cylinders 10 and 10a.

The exhaust passages or passageways include bores or passages 40, 40e, 40f, 40c,40d, 30d, 30e and outlet 301. The inner faces of bores40c and 40d are finished to provide sealsfor the exhaust valves 18 and 18a. Bores 40e and 40f are guides for the shaft portions `17p and l17q of valve body 17, and are finished to permit reciprocatory travel and sealing of passages 17c and 17e.

`Thus, it serves as the means to sepa-rate inlet passages 3%)b and 30e for the working fluids from exhaust fluid passages 30d `and 30e.

From FIGS. 1 and 2, the construction of the working components of the improved reversing valve is clearly shown. The valve body 17 has an enlarged portion 17s, about its center line, which Iforms a plug valve for sealing passages 30a, 30e and 30b. The reduced portions 17p and 17g are of equal length and the surfaces are finished to permit reciprocating travel and sealing. The outer ends 17m and 1711 are reduced to form shoulders 17g,7 and 17h and toreceive exhaust valves 18 and 18a and sleeves 20 and 21. The ends are threaded for nuts 22 and 22a, or other suitable fixtures. The valve body '17 .includes an axial center lbore 17b extending therethrough. The bore '17b is larger `than the diameter of shaft y15.

Passage 17a extends from center bore 17b, through the outer diameter of the enlarged portion 17s. Passages 117e and 17d are disposed on one extended end of valve body 17 and passage-s 17e and 17f are disposed, in matching positions, on the other extended kend of the valve body. Exhaust valves 18 andi 418a encompass the reduced portions 1711 and 17m olf valve body 17, and are pressed inwardly to butt against shoulders 17g and 17h of valve body 17, being held in xed positions by sleeves and 20a and nuts -22 and 22a. The notches or drilled ho-les 20c provide passages from 17d and 17j into the region between valve 18 and its associated piston 19, as Well as between v-alve l1811 and piston 19a. Sleeves 20 and 20a are fixed by the retaining nuts 22 and 22a with the inner portions of these nuts encompassing sealing rings 21 and 21a to allow shaft 15 reciprocatory travel.

Pistons 19 and 19a are contained in the inner circumference of valve cylinders 18 and 18a and encircle sleeves 20 and 20a. The pistons slide on the respective sleeves, in sealing contact therewith. The travel of pistons 19 and 19a is limited by retaining nuts 22 and 22a on one side and by exhaust valves 18 and 18a on their other sides.

The pistons 19 and 19a are moved outwardly toward the nuts 22 and 22a, by pressure applied through passages 30a, 17a, 17b, 20c and 17d, for piston 19, and passages 30a, 17a, 17b, slot corresponding to 20c, and 17f for piston 19a. Pistons 14 and 14a alternately contact pistons 19 and 19a to force them into valves 18 and 18a thereby exhausting the luids between the pistons 119 and 19a and their -associated valves. The exhaust passages for piston 19 include 20c, 17d, 17b, and 17C to open into 30d and 307i. The exhaust passages for piston 19a include the slot corresponding to 20c, 17f, 17b, and 17e to open into 30e and 307.

The partition structure 30 includes a central bore 40, 40a and 401) Which act as a composite cylinder about the enlarged plug-like portion y17s of valve body 17. The plug portion 17s may be moved beyond the center opening 30a in either direction, thereby closin-g passage 17a and also either of passages 40e, 30a` and 401, 30b. The inlet valve faces, formed by the smaller bores 40a and 40h, are iinished to senve as faced seats to allow the enlarged plug-like portion 17s to seal thereagainst. Bores 40e `and 40f are of smaller diameter and encompass the shaft portions 17g and 17p of valve body 17 to serve as guides for the Valve body 17, as well as a a closure for passages 17c and 17e. The enlarged portion 17s thus separates the working fluid inlet passages 30b and 30C from exhaust uid passages 30d and 30e. Bores 40e and 40d on the outer extremities of partition 30, encircle exhaust valve cylinders 18 and 18a to form closures therewith which include angular passages 30d and 30C. Common exhaust passage 30f connects 30d and 30e to a line (not shown).

Passage 30a serves as the inlet passage for working iluids, and the enlarged plu-g portion 117s serves as a portion of the inlet valve means. It will be appreciated that exhaust valves 18 and 18a comprise the exhaust valve means.

The oper-ation of the device o-f the invention will next be described. Assume the valve body 17 is in its center position (as seen in FIG. 4), effecting the closing of bore 40, then working uid is allowed to enter valve passage 17a and lls bore 17b and passages 17e` and 17e as, these passages are closed by bores 40e and 401. The luid therefor flows out passages 17d and 17]t and through notched sleeves 20 and 20a, entering into the cavities formed by exhaust valve cylinders 18a and 18 encompassing val've pistons 19 and 19a. Piston 19a is in its expanded position, but piston 19 is in its collapsed position and is free to move Iin an outward direction, against piston 14. The valve body 17 is now ready to move to the left, as further right hand movement cannot be made. As pistou 19a is already at its extreme movement position, then the pressure is eiective at piston 19 to expand its cavity, forcing exhaust valve 18 and valve body 17 t-o the left, opening the inlet passages to the right and opening the exhaust passages to the left to the positions of FIG. 5.

Since, as described in the construction details, the exhaust valves `18 and 18a are fastened secu-rely to valve body 17, any motion of either valve 18 or 18a is therefore impartedto valve body 17. When valve body 17 moves to the left, it allows working fluid to llow into bore 40, which aids in pushing enlarged portion 17s to its left hand position to close exhaust passage 30C. A mere cracking of the inlet passage to -bore 40 immediately fully actuates the valve.

Bore 40 allows working fluids to pass through bore 40a and passage 30b, thus allowing working fluids to the interfaces of piston 14 to move it to the right during movement of valve body 17 t-o the left. The same motion of valve 4body 17 opens the exhaust valve connections on the opposite side (for piston 14a) by moving valve 18a out of bore 40C opening the lefft hand cylinder to exhaust as piston 14a is draiwn to the right by movement of piston 14 to the right, through the interconnecting rod 15. This motion further closes valve 17 in bore 40 to inlet passage 30C.

As piston 14 nears the completion of its power stroke, piston 14a contacts its moveable piston 19a and collapses the chamber between 18a and 19a. The chamber iluid is exhausted into bore 17b by way of the notch corresponding to 20c and passage 17]L (now in communication) and thence out passage 17e, 30e and 30f. Further movement of the pistons moves the whole valve body 17 to the center position, depicted in FIG. 1.

The operation for powering piston 14a is the same as previously described for piston 14. The positions of the components during the power stroke for piston 14a and the simultaneous exhaust or non-power stroke for piston 14 are shown in FIG. 6.

In the foregoing, defining of actuation of specic mechanism denoting motions necessary has been fullled to show the complete cycle of the motor compressor unit and therein when each cycle is complete another one of like operation will ensue whereby a continuation of cycles, deemed known as reciprocatory movement is provided.

It will now be appreciated that an important feature of this invention resides in the provision of a self-reversing valve, in which a single operating valve means controls both intake and exhaust passage opening and closing, in order to insure positive operation at all times, by unitizing both intake and exhaust passages. Therefore the operating valve of this invention may be described as being a duplex compound valve with automatic start, being duplex because it controls two intakes and two exhausts and being compound because it operatively controls two pistons.

As many changes could be made carrying out the above principles of operation without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A motor-compressor unit incorporating a self-operating reversing Valve comprising, in combination opposed cylinder means; partition means disposed in the motor portion of the unit and separating said cylinder means and including inlet and exhaust passages for Working luid from a source of uid to a fluid exhaust via the said cylinder means; a pair of pistons respectively disposed in the: cylinder means and each having an inner face and an outer face; connecting means coupling the pistons together' for simultaneous movement with the inner faces comprising the motor portion of the unit and the outer faces com-. prising the compressor portion of the unit; said cylinder means each having connections for suction and discharge. lines in communication with the outer face of the pistons;y

inlet valve operating means slideable in the partition means to open and close said inlet passages; chamber defining means carried by the valve operating means and disposed in each of the cylinder means to close the exhaust passages in the partition means; said chamber means each comprising iirst wall means and second wall means slideable relative thereto to expand and collapse the chambers; said pistons respectively collapsing said chambers during alternate strokes; said inlet operating valve including further passages to said chambers to open the collapsed chamber, thereby opening the opposite exchaust passage, and the associated inlet passage to reverse the power stroke.

2, A motor-compressor unit incorporating an automatic reversing valve having the capacity to move off dead center, comprising in combination cylinder means; a pair of opposed, spaced apart pistons respectively disposed in the cylinder means and each having an inner face and an outer faces; connecting means between the pistons with the inner faces comprising the motor portion of the unit and the outer faces comprising the compressor portion of the unit; said cylinder means each having connections for suction and discharge lines in communication with the outer faces of the pistons; inlet valving means adapted to direct the flow of working liuid to the cylinder means against the piston inner faces; said inlet valving means being moveable relative to the connecting means and the pistons; partition means disposed in the motor portion of the unit and including an inlet passage for working iiuid to drive one of said pistons in one direction and an inlet passage to the other of said pistons to drive it in the opposite direction, on alternate strokes; said inlet passages adapted to be alternately opened and closed by the inlet valving means; said partition means including exhaust passages from the cylinder means for each of said pistons; valve means carried by the inlet valving means and moveable by each piston for closing its associated exhaust passage in the partition means; further means forming chambers with said valve means and slideably carried by the inlet valving means to collapse the chambers under the control of the pistons; said inlet valving means including passages to each of said chambers for opening the collapsed chamber by working iiuid under the control of said inlet valving means when in dead center position to initiate reversal of the direction of movement of the inlet valving means and exhaust closing valve means relative to the direction of movement of the pistons thereby opening the exhaust passage for the piston not associated with said opened chamber.

3. A motor-compressor unit comprising in combination self-operating reversing valve means having an inlet for working fluid and an exhaust for the fluid; opposed cylinder means; valve housing partition disposed in the motor portion of the unit to separate said cylinder means and including inlet and exhaust passages for the working iiuid connectible to said inlet and exhaust; a pair of pistons each having an inner face and an outer face respectively disposed in the cylinder means; connecting means coupling the pistons together for simultaneous movement on alternate power strokes with the inner faces comprising the motor portion of the unit and the outer faces comprising the compressor portion of the unit; said cylinder means each having connections for suction and discharge lines in communication with the outer faces of the pistons; inlet Valve operating means slideable in the valve housing partition means to open and close said inlet passages in response to movement of the inlet operating means; chamber defining means respectively carried by the valve operating means in each of the cylinder means to open and close the exhaust passages in the valve housing partition means; said chamber means each `comprising a valve and a valve piston slideable relative thereto to expand and collapse its chamber; said valve pistons respectively collapsing its associated chamber by contact with its piston during its non-power stroke; and said inlet valve operating means adapted to selectively open passages to said chambers,

permitting the working iiuid to open the collapsed chamber through movement of the valve operating means relative to the valve piston of the opened chamber thereby reversing the direction of the valve operating means to open the exhaust passage for the piston other than the one associated with the opened chamber, whereby the inlet valve operating means is opened to the piston on its nonpower stroke to reverse the strokes.

4. An automatic reversing valve having the capacity to move oi dead center, comprising in combination cylinder means; a pair of opposed spaced apart pistons respectively disposed in the cylinder means; connecting means between the pistons; inlet valving means adapted to direct the flow of working iiuid to the pistons in the cylinder means; said inlet valving means being moveable relative to the connecting means and pistons; partition means including an inlet passage for working fluid to drive one of said pistons in one direction and an inlet passage to the other of said pistons to drive it in the opposite direction; said inlet passages adapted to be alternately opened and closed by the inlet valving means; said partition means further including exhaust passages from the cylinder means for each of said pistons; exhaust valve means carried by the inlet valving means and moveable by each piston for closing its associated exhaust passage in the partition means; further means forming chambers with said exhaust valve means and slideably carried by the nlet valving means to collapse the chambers under the control of the pistons; said inlet valving means including passages to each of said chambers for opening the collapsed chamber by working iiuid under the control of said inlet valving means when in dead center position to initiate reversal of the direction of movement of the inlet valving mean-s and exhaust valve means relative to the direction of movement of the pistons, whereby the exhaust valve means opposite the opened chamber is moved to open its exhaust passage and the inlet valving means is moved to open the inlet passage to the piston associated with the opened chamber.

5. A self-operating reversing valve comprising, in combination opposed cylinder means; partition means separating said cylinder means and including inlet and exhaust passages for working iiuid from a source of fluid to a iiuid exhaust via said cylinder means; a pair of pistons respectively disposed in the cylinder means; connecting means coupling the pistons together for simultaneous movement; inlet valve operating means slideable in the partition means to open and close said inlet passages; chamber deiining means carried by the valve operating means and disposed in each of the cylinder means to open and close the exhaust passages in the partition mean-s; said chamber means each comprising first wall means and second wall means slideable relative thereto to expand and collapse the chambers; said pistons respectively collapsing said chambers during alternate strokes; and said inlet operating valve including further passages to said chambers to open the collapsed chamber thereby moving the valve operating means to open the inlet passage to the piston associated with the opened chamber and to open the exhaust passage for the other piston.

6. A self-operating reversing valve of a type having an inlet for working iiuid and an exhaust for the fluid comprising, in combination opposed cylinder means; valve housing means separating said cylinder means and including inlet and exhaust passages for the working fluid connectible to said inlet and exhaust, a pair of pistons respectively disposed in the cylinder means; connecting means coupling the pistons together for simultaneous movement of alternate power strokes; inlet valve operating means slideable in the housing means to open and close said inlet passages upon movement thereof; chamber defining means respectively carried by the valve operating means in each of the cylinder means to open and close the exhaust passages in the housing means; said chamber means each comprising a valve and a valve piston slideable relative thereto to expand and collapse its chamber; said pistons respectively collapsing its associated chamber during its non-power stroke by moving its valve piston; and said inlet valve operating means adapted to open passages to said chambers permitting the working fluid to open the collapsed chamber through movement of its valve piston relative to the valve operating means, opening the inlet passage to the piston associated with the opened chamber and opening the exhaust passage associated with the other piston.

7. A self-operating reversing valve adapted to operate opposed interconnected pistons disposed in opposed cylinders for simultaneous lmovement through alternating power strokes, comprising in combination a partition housing for operating the opposed pistons and a valve body moveable in the partition housing to apply working fluid to the pistons alternately; expandable and collapsible cham- 'ber forming means respectively carried by the valve body in the cylinders containing each of said pistons; said partition and valve body defining multiple passage between a -source of working fluid and an exhaust therefor; said passages including at least: one inlet passage for working fluid to each cylinder, one exhaust passage for the fluid from each cylinder, one inlet passage for working iluid to each chamber, and one exhaust passage for the fluid from each chamber; said pistons, under control of working fluid, sequentially collapsing their associated chambers on their non-power strokes and moving the valve body to close their respective inlet and exhaust passages; said valve body, when moved to dead center position, directing working fluid to expand the then collapsed chamber to further move the valve body thereby cracking said cylinder inlet passage to the piston associated with the expanding chamber and opening the exhaust passage 4for the -opposing cylinder; said valve body, responsive to working uid and lmovement thereof by the expanding chamber for closing the inlet passage to said opposing cylinder and opening the inlet passage to the piston associated with the expanding chamber, whereby cyclic operation is established to alternate the power stroke-s for said pistons.

8. The valve of claim 7 wherein the valve body comprises an elongated cylindrical shaft having a central enlarged peripheral portion with end portions for receiving the chamber forming means; said shaft including an axial passage; said enlarged portion including passages from its periphery in communication with the axial passage; said shaft further including pas-sages to its periphery from the axial passage.

9. The valve of claim 8 wherein the partition housing is cylindrical and includes a bore to receive the shaft in sliding sealing engagement; said partition bore having a central enlarged diameter regions to receive the enlarged peripheral portion of the shaft in sliding sealing engagement; certain of said further passages in the shaft opening into said chamber means respectively and others of said further passages being closed by the walls of the partition bore except when the shaft is moved to either exhaust position to open at least one selected passage.

10. The valve of claim 9 wherein the chamber forming means comprises cup-shaped exhaust valves carried thereby; exhaust valve pistons slideable within the cup-shaped exhaust valves to expand and collapse the chambers.

111. A self-operating reversing valve adapted to operate opposed interconnected pistons disposed in opposed cylinders for simultaneous movement through alternating power strokes, comprising in combination a partition housing for operating the opposed pistons and a valve body moveable in the partition housing to apply working fluid to the pistons alternately; expandable and collapsible chamber forming means respectively carried by the valve body in the cylinders containing each of said pistons; said partition and valve body defining passages between a source of working fluid and an exhaust therefor; said passages including inlet passages for working iluid to each cylinder, exhaust passages for the fluid from each cylinder, passages for working fluid to each chamber, and exhaust passages for the fluid from each chamber; said pistons, under control of working fluid, sequentially collapsing their associated chambers and moving the valve body to close 4their respective exhaust and inlet passages, on their nonpower strokes; said valve body, when moved to dead center posit-ion, directing Working fluid to expand the then collapsed chamber and open the inlet passage to the piston associated with the expanding chamber and opening the exhaust passage for the opposing cylinder and piston, whereby cyclic operation is established to alternate the power strokes for said pis-tons.

12. A self-operating reversing valve of a type adapted to operate opposed pistons contained in opposed cylinders for simultaneous movement with alternate power strokes, comprising in combination a partition housing for separating the opposed cylinders and a valve body moveable in the partition housing to apply working fluid to activate the pistons alternately; chamber forming means carried by the valve body and associated with each of said pistons; said partition and valve body dening at least one inlet passage to each cylinder, at least one exhaust passage from each cylinder, at least an inlet passage to each chamber lof the chamber forming means, and at least an exhaust passage from each chamber; each of said pistons adapted to collapse its associated chamber durings its exhaust stroke, through contact therewith to close its exhaust passage when the valve body is in dead center position; said partition and v-alve body dening at least one passage for inlet working uid to the collapsed chamber on dead center position of the valve body to effect expanding of the collapsed chamber by working iiuid and further move the valve body; the valve body, upon expansion of its collapsed chamber, moving to open the inlet passage to the piston associated with the collapsed chamber to insure its power stroke; said valve body upon said movement opening the exhaust passage to the other piston whereby cyclic operation is insured to alternate power strokes for said pistons.

References Cited by the Examiner UNITED STATES PATENTS 109,167 11/1870 Ambos 91-329 1,241,783 10/1917 Tocknell 91--329 1,441,017 1/ 1923 Mattson et al. 91-329 2,370,068 2/ 1945 Palrn 91--329 SAMUEL LEVINE, Primary Examiner.

P. E. MASLOUSKY, Assistant Examiner. 

1. A MOTOR-COMPRESSOR UNIT INCORPORATING A SELF-OPERATING REVERSING VALVE COMPRISING, IN COMBINATION OPPOSED CYLINDER MEANS; PARTITION MEANS DISPOSED IN THE MOTOR PORTION OF THE UNIT AND SEPARATING SAID CYLINDER MEANS AND INCLUDING INLET AND EXHAUST PASSAGES FOR WORKING FLUID FROM A SOURCE OF FLUID TO A FLUID EXHAUST VIA THE SAID CYLINDER MEANS; A PAIR OF PISTONS RESPECTIVELY DISPOSED IN THE CYLINDER MEANS AND EACH HAVING AN INNER FACE AND AN OUTER FACE; CONNECTING MEANS COUPLING THE PISTONS TOGETHER FOR SIMULTANEOUS MOVEMENT WITH THE INNER FACES COMPRISING THE MOTOR PORTION OF THE UNIT AND THE OUTER FACES COMPRISING THE COMPRESSOR PORTION OF THE UNIT; SAID CYLINDER MEANS EACH HAVING CONNECTIONS FOR SUCTION AND DISCHARGE LINES IN COMMUNICATION WITH THE OUTER FACE OF THE PISTONS; INLET VALVE OPERATING MEANS SLIDEABLE IN THE PARTITION MEANS TO OPEN AND CLOSE SAID INLET PASSAGES; CHAMBER DEFINING MEANS CARRIED BY THE VALVE OPERATING MEANS AND DISPOSED IN EACH OF THE CYLINDER MEANS TO CLOSE THE EXHAUST PASSAGES IN THE PARTITION MEANS; SAID CHAMBER MEANS EACH COMPRISING FIRST WALL MEANS AND SECOND WALL MEANS SLIDEABLE RELATIVE THERETO TO EXPAND AND COLLAPSE THE CHAMBERS; SAID PISTONS RESPECTIVELY COLLAPSING SAID CHAMBERS DURING ALTERNATE STROKES; SAID INLET OPERATING VALVE INCLUDING FURTHER PASSAGES TO SAID CHAMBERS TO OPEN THE COLLAPSED CHAMBER, THEREBY OPENING THE OPPOSITE EXCHAUST PASSAGE, AND THE ASSOCIATED INLET PASSAGE TO REVERSE THE POWER STROKE. 